The present invention relates to a method for electrochemical conversion of a material being insoluble in a fluid into a material being soluble in the fluid; an electrochemical reactor; an ion-selective electrolyte, an electrode, and a mixed ion-selective electrolyte, and electrode material for use when carrying out the method and for use in the electrochemical reactor, and use of the method and for use of the reactor for removal of soot particles from flue gases and oil in waste water.